A fuel cell-powered motorcycle is designed to run by rotating a drive wheel driven by a motor which in turn is driven with an electric power generated by a fuel cell installed therein. Conventional fuel cell-powered motorcycles include those equipped with a water-cooled fuel cell which can generate a relatively large electric power, and those equipped with an air-cooled fuel cell which can generate a relatively small electric power of, e.g., several kilowatts.
The air-cooled fuel cell, while it generates a relatively small power, has advantages such that it un-necessitates accessories, such as a radiator, a cooling water pump and a reservoir tank, required for the water-cooled fuel cell and it can utilize air as a reactant gas for also cooling the heat generated with the power generation. The air-cooled fuel cell has a low pressure loss through the air channel, and its cooling system has a simple structure requiring a fan as a sufficient accessory device instead of a compressor and can suppress the power consumption of the fan.
The fuel cell-powered motorcycle carrying such an air-cooled fuel cell introduces air as a reactant and also a coolant by means of a fan and supplies it to the fuel cell. More specifically, the air introduced into the fuel cell functions as an oxidant for electrochemically reacting with hydrogen as a fuel by the fuel cell, and also as a coolant for cooling the fuel cell. Thus, at the fuel cell, the heat generated with power generation is cooled with the air which is a reactant gas.
In fuel cell-powered vehicles including such a fuel cell-powered motorcycle, it has been tried to dispose a hydrogen sensor in the vehicle body for the purpose of mainly for detection of hydrogen leaked from a fuel tank and a fuel-cell stack and improve the system. For example, Patent document 1 has proposed to install a hydrogen sensor in an upper corner of a tank housing which stores a fuel tank and provide a ventilation pipe exit from a fuel cell, thereby aiming at detecting hydrogen leaked out of the fuel tank and the fuel-cell stack with a single hydrogen sensor. Patent document 2 has proposed installing a fuel cell in a fuel-cell storage case, and installing a hydrogen sensor in an air pipe connecting a compressor (blower) with the storage case. However, the application of these systems to an air-cooled fuel cell-powered motorcycle involves severe problems accompanying the accommodation of the fuel cell (or the exhaust section thereof) within a housing case for the fuel tank or the fuel cell, that is, 1) the fuel cell system becomes complicated, thus spoiling the strong point of the air-cooled fuel cell, i.e., a simplified fuel cell system because of omission of a cooling water passage, and 2) it makes difficult the realization of the fundamentally advantageous performance of the air-cooled fuel cell-powered motorcycle of improved exhaust efficiency attained by reduction of air passage resistance while omitting a compressor.
On the other hand, Patent document 3 has proposed an air-cooled fuel cell-powered motorcycle wherein a fuel cell and a hydrogen tank are arranged in this order along a passage of air introduced from the front of vehicle body, and hydrogen sensors are disposed before and after the hydrogen tank, thereby improving the detection of hydrogen leaked into the body. According to our study, however, the above-mentioned layout has made it impossible to attain the improvement in efficiency of exhaust from the fuel cell due to the presence of the hydrogen tank arranged after the fuel cell and also fails in early detection of a malfunction occurring in the fuel cell stack.